This article proposes a tentative framework to support empirical analysis of portfolios as pedagogical tools for formative and summative assessment in higher education. It aims to get a deeper understanding of the role of the portfolio in student learning both as a tool and as representations of this tool. To that end, we use three sets of theoretical ideas: Wartofsky's conceptualization of perception through the creation of artifacts, actor-network theory, and Wertch's notions of internalization, appropriation and mastery. This article is meant to complement current portfolio research with an original approach that addresses explicitly epistemological questions and concepts like learning and knowledge and explores possible avenues for analyzing and understanding portfolios as artifacts and tools in learning activities. (Contains 3 footnotes.)